Each year, children wander away from their parents and often become lost, some times for a considerable period. Not infrequently, a child will stray from its home or separate from a parent at a store or park, causing great anguish and concern. Occasionally, criminals abduct children for nefarious purposes, prompting fear of possible harm. Adults who suffer from loss of memory, especially those who suffer from Alzheimer's disease, also become lost from relatives or caregivers giving rise to worries that such individuals may suffer harm.
Once a child or adult becomes lost, public safety personnel incur the task of locating that person. Often, such public safety personnel, sometimes aided by volunteers, spend countless hours searching for the missing child or adult. In some instances, delays in locating a missing individual can prove tragic once the missing individual's surroundings becomes unsafe, either as a result of a criminal act of another, or as a result of a dangerous natural environment. Thus, prompt location of the missing individual is critical.
Various schemes exist for locating individuals once they become lost or missing. U.S. Pat. No. 5,021,794, issued Jun. 4, 1991, in the name of Robert Lawrence, discloses a personal emergency locator system that includes an UHF transceiver carried by an individual whose location is of interest. Should the individual wearing the transceiver become lost, then a parent, caregiver, or other concerned person uses the public switched telephone network to communicate with a signal repeater. Once in communication with the signal repeater, the parent, caregiver, or concerned seeking to locate the missing child or adult actuates a signal generator that produces a coded signal carried by the PSTN to the repeater for broadcast. Upon receipt of the signal broadcast by the repeater, the receiver portion of the UHF transceiver carried by the missing individual triggers the transmitter portion of the transceiver to broadcast a homing signal for tracking by public safety personnel using direction-finding receivers in their vehicles.
The Lawrence '794 patent incurs several drawbacks. First, the UHF transceiver carried by the missing person is an "active" device that requires a DC power source, in the form of a battery, for operation. Once the battery becomes depleted, the transceiver loses its ability to broadcast a homing signal. Second, with the Lawrence locating system, the individual seeking to locate the missing child or adult must possess a signal generator to generate the coded signal broadcast for receipt by the transceiver carried by the missing child or adult. Absent such a signal generator, the individual seeking to locate the missing person cannot actuate the transceiver on the missing person to transmit the homing signal.
Thus, there is a need for a technique for locating a missing child or adult that overcomes the aforementioned disadvantages of the prior art.